<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>


    <script src="js/jquery_1.9.js"></script>
<body>
1


</body>
<script>
alert("OK1")
var checkNum = /^[A-Za-z0-9]+$/;
if(checkNum.test("1")){
    alert("1")
}else{
    alert("2")
}
alert("3")
</script>
</html>